The third generation (or “3G”) of wireless communication services promises to bring unity to a fractured worldwide cellular market. 3G systems will permit seamless travel not presently available in the splintered U.S. mobile telephone service. In addition, 3G systems promise a wide array of high-speed broadband data transmission and processing, including video, on-board navigation, and Internet access.
One wireless standard designed to support 3G services is cdma2000™, defined by the ITU in its IMT-2000 vision. Phase one of the cdma2000 standard effort, known as “1×RTT” (i.e., Radio Transmission Technology), has already been completed and published by the Telecommunications Industry Association (TIA). 1×RTT refers to cdma2000 implementation within existing spectrum allocations for cdmaOne—1.25 MHz carriers. The technical term is derived from N=1 (i.e., use of the same 1.25 MHz carrier as in cdmaOne) and the “1×” means one time 1.25 MHz. 1×RTT is backward compatible with cdmaONE networks, but offers twice the voice capacity, data rates of up to 144 kbps, and overall quality improvements.
Also employing a 1.25 MHz channel is the High Data Rate (HDR) technology. HDR is RF compatible with cdmaOne and 1sRTT systems and permits side-by-side deployment of transmitters and antennas in existing CDMA towers. Unlike 1×RTT, which is optimized for circuit switched services, HDR is spectrally optimized for best effort packet data transmission. HDR delivers very high-speed CDMA wireless Internet access at peak data rates greater than 1.8 Megabits per second. Notably, unlike 1×RTT, the control and data channel in an HDR carrier are time multiplexed.
Because of its high speed Internet access, it is preferable to conduct data calls over an HDR carrier, rather than on a 1×RTT carrier. Nevertheless, because HDR is packet based, it does not accommodate real time applications very well. Thus, a user of an HDR carrier who wishes to place a voice call would need to use a carrier such as 1×RTT.
Thus, there is a need in the art for a hybrid wireless system, which allows calls to be transferred between a 1×RTT carrier and an HDR carrier, as circumstances dictate.